Method and apparatus for producing corrugated tubing

ABSTRACT

A method and apparatus for producing corrugated metal tubing. The apparatus comprises a series of rolls which guide and propel the tubing through a final patterning means which produces the desired corrugations. The corrugated tubing so produced has desirable mechanical and heat transfer properties and is visually appealing.

United States Patent Laws [ Dec. 30, 1975 METHOD AND APPARATUS FOR PRODUCING CORRUGATED TUBING [75] Inventor: Harold H. Laws, East Alton, Ill.

[73] Assignee: Olin Corporation, New Haven,

Conn.

[22] Filed: Mar. 28, 1975 [21] Ap l. No.: 563,034

[52} US. Cl 72/178; 72/l80 [51] Int. Cl. B21D 13/04 {58] Field of Search 72/178, 180, 224

[56] References Cited UNITED STATES PATENTS 1,777,728 10/1930 Kumpf 72/178 X Primary ExaminerMilton S. Mehr Attorney, Agent, or FirmDavid A. Jackson; Robert H. Bachman [57] ABSTRACT A method and apparatus for producing corrugated metal tubing. The apparatus comprises a series of rolls which guide and propel the tubing through a final patterning means which produces the desired corrugations. The corrugated tubing so produced has desirable mechanical and heat transfer properties and is visually appealing.

10 Claims, 5 Drawing Figures ,wQQOQ QVQI wvwqbk QMEQMKRTQ Qvmm EE E85 MJQQQ WAERN REMQQRMQ US. Patent Dec. 30, 1975 Sheet 2 of3 Sheet 3 of 3 US. Patent Dec. 30, 1975 METHOD AND APPARATUS FOR PRODUCING CORRUGATED TUBING BACKGROUND OF THE INVENTION Corrugated tubing has many benefits and applications. The addition of corrugations such as longitudinal grooves to tubing makes it more rigid and resistant to denting. The increased surface area which results from the formation of corrugations improves the heat transfer properties of the tubing and is of value in heat exchange applications. Finally, corrugated tubes have aesthetic value and find a wide variety of uses such as curtain rods, towel bars and the like.

Past methods for producing corrugated tubing have all involved some additional operation such as drawing or swaging and have, consequently, been economically unattractive.

SUMMARY OF THE INVENTION The present invention comprises a method and an apparatus for producing corrugated tubing. The method and apparatus of the present invention are particularly adapted to produce corrugations in tubes prepared from metal strip formed into tubular shape and welded at the abutting longitudinal edges thereof. The apparatus of the present invention is easily adapted for the preparation of tubing possessing a wide variety of corrugations.

The apparatus of the present invention consists of a series of rolls particularly adapted for use in connection with a tube mill of the type used to produce welded tube from strip.

The method and apparatus of the present invention permit the formation of corrugated tubing of various shapes without the necessity of employing time-consuming drawing or swaging operations. Tubing prepared in accordance with this invention is uniform in cross section and is more resistant to surface damage, such as buckling or denting.

Accordingly, it is principal object of the present invention to provide a simple method for the fabrication of metallic tubing having corrugations.

It is a further object of the present invention to provide a method as aforesaid wherein said tubing is provided with corrugations after its formation.

It is yet a further object of the present invention to provide a method and apparatus as aforesaid which is less time-consuming and results in products possessing greater structural uniformity.

Other objects and advantages will become readily apparent from the detailed description which follows with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows in schematic form the arrangement of the rolls which comprise the apparatus of the present invention.

FIG. 2 shows in perspective a preferred embodiment of the apparatus of the present invention.

FIG. 3 shows an alternate embodiment of the present invention adapted for the preparation of spirally grooved tubing.

FIG. 4 depicts tubing prior to entering the apparatus of the present invention.

FIG. 5 shows a typical final product of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus of the present invention consists of a plurality of shaped rolls which are employed in conjunction with an apparatus for the preparation of tubing from metal strip. Such a tube mill may employ a tube welding apparatus such as that disclosed in US. Pat. No. 3,037,105, to Kohler, wherein the longitudinal edges of an open tube formed from strip are welded together by high frequency induction welding. The rolls of this invention are placed after the sizing section of the aforenoted welding apparatus, and are, thus, able to handle the tubing immediately after its formation. These rolls have a cylindrical shape and have a concavity in the cylindrical surface having a radius equal to the radius of the tube which is to be corrugated. These rolls may be classified into five groups, those being, idling rolls, resilient drive rolls, steel drive rolls, turks head rolls and patterned turks head rolls. The spatial arrangement of these rolls is schematically illustrated in FIG. 1.

The apparatus of the present invention is shown in perspective in FIG. 2, wherein'a preferred embodiment of the present invention is illustrated. The tubing to be corrugated, T, enters the apparatus, as shown in the left-hand corner of the figure. As the tubing T enters the apparatus, it passes through alternating pairs of idling rolls 1 and resilient drive rolls 2 which are located in planes removed from each other. It is not critical whether the first set of rolls are resilient drive rolls or idling rolls. Each idling roll and resilient drive roll has a concave surface 3 machined in its cylindrical face corresponding to about one-half of the cross-sectional shape of tubing T. The cylindrical surfaces 4 of each of the members of the pairs of rolls immediately adjacent concave surfaces 3 contact the corresponding surface on the mating roll. Thus, each pair of idling rolls 1 and each pair of resilient drive rolls 2 defines an opening having dimensions approximately equal to the cross-section of the tube. Both idling rolls 1 and resilient drive rolls 2 have a similar shape although their construction and function are different. The concave surfaces 3 of resilient drive rolls 2 are composed of a resilient substance such as rubber or urethane so as to maximize the coefficient of friction between the rolls and the tubes. The resilient drive rolls 2 are driven by a drive means not shown which may conveniently be an electric motor in conjunction with conventional power transmission means such as gears, chains and belts. The function of the resilient drive rolls 2 is to propel the tube T through the apparatus. The resilient drive rolls 2 are conveniently, though not necessarily, located in a single plane.

Alternating with the resilient drive rolls 2 are a plurality of idling rolls 1, perferably located in a plane removed 90 from the plane of said drive rolls. Idling rolls 1 are preferably constructed of a non-resilient material, and serve to accurately locate the tubing and prevent it from bowing or buckling as it passes through the drive rolls. Generally, the total number of idling rolls corresponds to that of the drive rolls, as sets of each cooperate in minimizing distortion at sustained high speed operation of the apparatus. The actual number of sets of drive rolls and idling rolls is not critical, however, the number of resilient drive rolls 2 employed must be adequate to transmit the required amount of force to the tubing T so as to cause it to pass through the remainder of the apparatus. The number of sets of idling rolls 1 is preferably one greater than the number of sets of resilient drive rolls 2, so as to accomodate the presence of a set of non-resilient drive rolls, discussed hereinbelow.

After tube T emerges from the last idling roll 1, it enters a set of non-resilient drive rolls 5 which serve both to propel and size the workpiece. Thus, upon issuing from drive rolls 5, tubing T is shaped to the exact diameter desired. Non-resilient drive rolls 5 are preferably constructed of a hard metallic material such as steel, and possess a general size and shape corresponding to that of the resilient drive rolls 2. This set of non-resilient drive rolls 5 is preferably located in the same plane as the resilient drive rolls 2.

Following the set of non-resilient drive rolls 5, the tubing passes through a set of smooth turks head rolls 6 which assure straightness of the tube. A set of turks head rolls comprises four rolls, located in two orthogonal planes, such that the centerline of the incoming tube passes through the intersection of the orthogonal planes. Each roll has a groove 7 machined in its cylindrical surface having a radius equal to the radius of the tube T, and each of the rolls in the turks head 6 contacts one-fourth the circumference thereof.

Upon passing through the set of smooth turks head rolls 6, the tubing passes through a set of patterned turks head rolls 8. The patterned turks head rolls 8 are machined so as to have a surface configuration corresponding to the mirror image of the desired surface configuration of the finished tube T. Turks head rolls 8 may, forexample, define a plurality of longitudinally extended, equidimensioned corrugations such as are illustrated in FIG. 2. It is to be understood, however, thatthe present invention is not limited thereby, as a wide variety of surface configurations may be defined on rolls 8 as are well known in the art. Thus, the invention includes such variations in surface configuration as spiral indentation, which will be discussed in greater detail hereinbelow.

Subsequent to the patterned turks head rolls 9 the tubing may pass through or on a set or sets of supporting rolls, but these further rolls are of a completely conventional nature, and form no part of the present invention.

The apparatus and process of the present invention may be applied to tubing made of almost any metallic material, however, properties of the material from which the tube is made influence the characteristics of the process. Tubing materials which have been found to be particularly satisfactory include brass and other copper alloys, aluminum and low carbon steel. In general, the process of the present invention is applicable to tubing of any diameter, however, it is preferred that the diameter of the tubing be less than 6 inches and it is most preferred that the diameter of the tubing be from 0.5 to 2 inches.

The process of the present invention is most applicable to thin wall tubing, that is to say, tubing in which the wall thickness is less than 10% of the diameter. It will be found that tubes having thick walls and tubes made of high strength materials will be more difficult to process by this invention than thin wall tubes or tubes made of softer material. If this process is to be applied to thick wall tubes made of relatively strong materials, additional drive rolls may be necessary to propel the tube through the apparatus and the maximum obtainable corrugation depth may be limited. Welded tubing as well as seamless tubing may be processed with the present apparatus. One of the advantages of using welded tubing is that there is essentially no limit on the length of the tube in which the corrugations may be formed. This lack of length limitation is particularly true when the apparatus of the present invention is used in conjunction with a tube mill which produces welded tubing from metal strip. Although the preceeding discussion has assumed that the tubing to be processed has circular ciruclar cross-section, the process of the present invention is applicable to tubes having other cross-sections, such as oval. Of course, if tubing having a non-circular cross-section is to be processed, appropriately contoured rolls must be employed.

The depth of the corrugations produced by the present invention generally range from 0.5 to 3 times the wall thickness of the tubing.,Attempts to form corrugations having depths much in excess of 3 times the wall thickness will result in collapse of the tubing. The width of the corrugation at the outer surface of the tube will generally range from 0.5 to 2 times the depth of the groove. A wide variety of shapes are possible, however, it is not practical to produce corrugations such as grooves having small internal radii. In general, any internal radiusmust be greater than 0.2 times the wall thickness. The number of grooves produced will generally range from 4 to 40.

As noted earlier, a wide variety of geometrical configurations of corrugations may be produced by the apparatus and process of the present invention. The simplest of these configurations comprise straight grooves, discussed above, wherein the grooves produced are straight and parallel to the axis of the tubing. Spiral grooving mayalso be produced in which the grooves spiral about the axis of the tube. The lead or the distance between identical points on the spiral, in the direction of the tube axis will commonly range from 0.1 to 10 times the diameter of the tube. Spiral grooving has particular advantages in heat transfer applications.

In the production of spirally grooved tubing, it is preferred that the patterned turks head rolls be replaced by a plurality of grooving tools which are slightly canted and mounted in a free-floating enclosure cluster. FIG. 3 shows a preferred embodiment for the structure and arrangement of the grooving tool and associated enclosure cluster. Thus, spiral grooving apparatus 9 is shown which comprises a grooving tool 10 supported by a rotatabletool holder 11 which, in turn, is mounted upon headmember .12. Head member 12 is supported and adapted for free-floating rotation within bearing housing 13, by two tapered roller bearings, not shown, located therein. Only one grooving tool is depicted for purposes of illustration alone, as the apparatus may include as 'many such tools as are physically possible to employ, space being the only limitation thereon.

In practice, grooving tool 10 is disposed at an angle to the longitudinal direction of tube T which thereby defines the pitch of the resulting spiral. It has been found that the maximum angle that can be employed between the longitudinal direction of T and grooving tool 10 ranges from 30-35, as, beyond that point, the tool ceases to function and begins to skid on the tube. Naturally, the direction of the spiral may be controlled by the placement of tool 10, so that either right-hand or left-hand spirals may be produced.

In practice, apparatus 9 would be located in place of patterned turks head rolls 8 depicted in FIG. 2. As tube T passes through head member 12, grooving tool would impress the appropriate pattern or groove. Though grooving tool 10 is depicted in the formation of grooved tubing, it would be possible, and, therefore, within the scope of the present invention, to employ a tool possessing a pattern of differing configuration which would then be applied to tube T in a spiralling direction.

As stated earlier, apparatus 9 is employed as a freefloating arrangement and, as such, is not power-driven. A certain instance may obtain, however, where power actuation may be required. Specifically, where the angle of the pitch of the spiral and the diameter of the tube are such that the longitudinal distance traveled by tool 10 on tube T in order to complete one revolution therearound, known as the lead, is less than /2 inch, it would be necessary to drive apparatus 9 in relation to the linear speed of tube T. When the lead equals or exceeds however, apparatus 9 may be employed in free-floating operation.

FIG. 4 shows a section of welded tubing prior to entering the present apparatus. The tubing has a slightly oval cross-section domonstrated by cross-section 14 which is a result of the forming operations which produced the tube. The outside diameter of the tubing is slightly greater than the desired outside diameter of the finished product. This is generally necessary since the tubing usually suffers from reduction as it passes through the multiple rolls of the present invention. In general, the tubing will suffer a reduction of from I to 10% in outside diameter as it passes through the apparatus of the present invention. If the rolls of the apparatus are properly contoured, tubing which is slightly oval may be converted to circular tubing.

FIG. 5 shows the tubing of FIG. 2 after it has passed through the apparatus of the present invention. The finished tubing has 16 grooves and has a final diameter of about 5% less than the starting diameter.

The apparatus presented in the accompanying figures is merely illustrative of the concepts of the present invention and should not be construed as limiting thereof.

It is to be understood that the invention is not limited to the illustrations described and shown herein, which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are suitable of modification of form, size, arrangement of parts and details of operation. The invention rather is intended to encompass all such modifications which are within its spirit and scope as defined by the claims.

What is claimed is:

I. An apparatus for providing a longitudinally extended pattern on a metallic tube comprising:

A. a plurality of paired idling rolls, each roll of said pair possessing a continuous concave surface of semi-circular cross section located in the cylindrical surface thereof and both rolls located within the same plane;

B. a plurality of paired resilient drive rolls located in adjacent alternation with said idling rolls and in a plane perpendicular to the plane of said idling rolls, and possessing concave surfaces identical thereto, wherein said concave surfaces are lined with a resilient material;

C. at least one pair of non-resilient drive rolls of identical configuration to said resilient drive rolls and located beyond said resilient drive rolls, serving to size said tube;

D. a set of 4 smooth turks head rolls situated beyond said non-resilient drive rolls, arranged in two orthogonal axial planes the intersection of said axial planes corresponding to the central axis of the tube, each of said rolls having a smooth concave surface of quarter-circular cross-section located in its cylindrical surface, and all of said rolls positioned so as to lie within a single plane perpendicular to the longitudinal axis of said tube; and

E. means for forming said pattern on said tube comprising at least one patterned roll located in contact with said tube after its passage through said smooth turks head rolls.

2. The apparatus of claim 1 wherein the total number of pairs of said idling rolls equals the sum of the total pairs of resilient drive rolls and non-resilient drive rolls, and said non-resilient drive rolls are located adjacent a pair of said idling rolls.

3. The apparatus of claim 1 further including drive means associated with all of said drive rolls, and said smooth turks head rolls to facilitate the continued movement of said tube therethrough.

4. The apparatus of claim 1 which is situated in axial alignment with the sizing section of an apparatus for the preparation of tubing from metal strip.

5. The apparatus of claim 1 wherein said forming means comprises a set of four patterned turks head rolls identical in structure and arrangement to said smooth turks head rolls which possess a plurality of projections provided in said concave surfaces corresponding in number and shape to the pattern to be formed in said tube.

6. The apparatus of claim 1 wherein said forming means comprises at least one grooving tool disposed in canted relationship to the longitudinal axis of said tubing which is adapted for rotation therearound.

7. The apparatus of claim 6 wherein said tool is mounted in a free-floating enclosure cluster comprising a tool holder mounted on a rotatable head member.

8. The apparatus of claim 7 wherein said forming means further includes drive means associated with said cluster.

9. The apparatus of claim 1 wherein said pattern comprises at least one groove.

10. The apparatus of claim 1 wherein said tubing is prepared from a material selected from the group consisting of copper base alloys, aluminum and low carbon steel. 

1. An apparatus for providing a longitudinally extended pattern on a metallic tube comprising: A. a plurality of paired idling rolls, each roll of said pair possessing a continuous concave surface of semi-circular cross section located in the cylindrical surface thereof and both rolls located within the same plane; B. a plurality of paired resilient drive rolls located in adjacent alternation with said idling rolls and in a plane perpendicular to the plane of said idling rolls, and possessing concave surfaces identical thereto, wherein said concave surfaces are lined with a resilient material; C. at least one pair of non-resilient drive rolls of identical configuration to said resilient drive rolls and located beyond said resilient drive rolls, serving to size said tube; D. a set of 4 smooth turk''s head rolls situated beyond said nonresilient drive rolls, arranged in two orthogonal axial planes the intersection of said axial planes corresponding to the central axis of the tube, each of said rolls having a smooth concave surface of quarter-circular cross-section located in its cylindrical surface, and all of said rolls positioned so as to lie within a single plane perpendicular to the longitudinal axis of said tube; and E. means for forming said pattern on said tube comprising at least one patterned roll located in contact with said tube after its passage through said smooth turk''s head rolls.
 2. The apparatus of claim 1 wherein the total number of pairs of said idling rolls equals the sum of the total pairs of resilient drive rolls and non-resilient drive rolls, and said non-resilient drive rolls are located adjacent a pair of said idling rolls.
 3. The apparatus of claim 1 further including drive means associated with all of said drive rolls, and said smooth turk''s head rolls to facilitate the continued movement of said tube therethrough.
 4. The apparatus of claim 1 which is situated in axial alignment with the sizing section of an apparatus for the preparation of tubing from metal strip.
 5. The apparatus of claim 1 wherein said forming means comprises a set of four patterned turk''s head rolls identical in structure and arrangement to said smooth turk''s head rolls which possess a plurality of projections provided in said concave surfaces corresponding in number and shape to the pattern to be formed in said tube.
 6. The apparatus of claim 1 wherein said forming means comprises at least one grooving tool disposed in canted relationship to the longitudinal axis of said tubing which is adapted for rotation therearound.
 7. The apparatus of claim 6 wherein said tool is mounted in a free-floating enclosure cluster comprising a tool holder mounted on a rotatable head member.
 8. The apparatus of claim 7 wherein said forming means further includes drive means associateD with said cluster.
 9. The apparatus of claim 1 wherein said pattern comprises at least one groove.
 10. The apparatus of claim 1 wherein said tubing is prepared from a material selected from the group consisting of copper base alloys, aluminum and low carbon steel. 